Although Bush administration officials have frequently lashed out at Syria and Iran, accusing it of helping insurgents and militias here, the largest number of foreign fighters and suicide bombers in Iraq come from a third neighbor, Saudi Arabia, according to a senior U.S. military officer and Iraqi lawmakers.

About 45% of all foreign militants targeting U.S. troops and Iraqi civilians and security forces are from Saudi Arabia; 15% are from Syria and Lebanon; and 10% are from North Africa, according to official U.S. military figures made available to The Times by the senior officer. Nearly half of the 135 foreigners in U.S. detention facilities in Iraq are Saudis, he said.

Fighters from Saudi Arabia are thought to have carried out more suicide bombings than those of any other nationality, said the senior U.S. officer, who spoke on condition of anonymity because of the subject’s sensitivity. It is apparently the first time a U.S. official has given such a breakdown on the role played by Saudi nationals in Iraq’s Sunni Arab insurgency.

He said 50% of all Saudi fighters in Iraq come here as suicide bombers. In the last six months, such bombings have killed or injured 4,000 Iraqis.

The situation has left the U.S. military in the awkward position of battling an enemy whose top source of foreign fighters is a key ally that at best has not been able to prevent its citizens from undertaking bloody attacks in Iraq, and at worst shares complicity in sending extremists to commit attacks against U.S. forces, Iraqi civilians and the Shiite-led government in Baghdad.

So why don’t we declare war on the Saudis? After all, their people are killing ours. Their people killed 3000 of ours on 9/11. Remember, it was the Saudi King that summoned our vice president. Summoned. Not requested, not invited. Summoned.